This is a linkpost for http://bearlamp.com.au/fish-oil-and-the-self-critical-brain-loop/
Another method that I have found effective in getting rid of the self-critical brain loop is asking myself "have I already learned the lesson of the mistake here?" If the answer is no, I use the technique you described of trying to figure out what the mistake(s) were that lead to the event and how I could fix them. However, I found that figuring this out alone did not stop the loop, so it is important that whenever the answer to the question becomes 'yes' to the question of whether you learned the lesson to enforce very strongly in your brain that there is nothing else useful to be learned here, I am wasting my time. This technique was harder the first few times, but once it became a habit for me I was able to start breaking the loop pretty easily just by logically showing myself that I was being stupid.
Muting the self-critical brain loop (and thanks for that terminology!) is something I'm very interested in. Have you investigated vegan alternatives to fish oil at all?
My impression is that algae oil is more similar to fish oil than flax, if you decide to experiment - it's where fish get their omega-3 from.
A. No I have not.
B. You need to check if it does something similar before assuming that it will. Then flax oil is an option. However there is a debate as to whether it is the same thing or causes the same effect or is absorbed the same way. (fish oil vs flax oil). I don't know your stance on krill oil either and I would look there too.
C. If the problem is bad enough, reconsider your dietary restrictions, speak to a professional or experiment with your intake.
I am pretty hesitant to stop taking the fish oil and run other tests given that I get 24-36 hours before I inevitably get bitten by a critical loop.